Michael Swain was attacked by the bull mastiff when he went to his neighbour's house to fetch his football as he played in his driveway with his brother Joseph, five. The dog's owner Tony Oxley waved the boy into his walled front garden, but when Michael knocked on the door the dog darted through the gap and pounced.
Michael's father Graham, 37, a builder, said at their home in Horton Bank Top, Bradford, West Yorkshire: "The same dog attacked my wife Sonya three years ago." She felt terrible now that she had not reported the attack.
He said Michael's left eye was saved by his glasses. "He is a typical kid who hates wearing glasses. Thank God he had them on at the time." He said he rushed outside when he heard screaming. "His face was dripping blood everywhere ... his jumper had been torn to shreds and his back was like a pepper pot with all the teeth marks. It is a horrendous dog. It is like a small horse."
He said: "Michael has been in a lot of pain but he is being very brave." He had joked before going into surgery at Bradford Royal Infirmary.
Mr Oxley, who lives with his wife Karen and their six-month-old baby, kept Casper in a fenced-in kennel in his back garden. He said: "I am absolutely devastated and heartbroken to loose Casper, but that's nothing to the feeling I have for Michael and his family. I'm so sorry about what has happened."
A fully grown bull mastiff weighs about 110-130 lbs and stands about 25-27 inches tall.
West Yorkshire Police said: "The owners have been reported for having a dog which was dangerously out of control. The owners agreed to have the dog destroyed. A report has been made to the Crown Prosecution Service"Reuse content